<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        div{
            width: 300px;
            height: 300px;
            border: 1px solid #000;
            margin: 50px;
            box-shadow: 5px 10px 10px 10px #999; 
        }
    </style>
</head>

<body>
    <div>
        这是一个div盒子
    </div>
</body>
</html>